In the electronic circuit component mounter disclosed in patent literature 1 below, a dropped component storage box is provided on a mounting head which holds a suction nozzle and is moved in the X-axis and Y-axis directions. The dropped component storage box is positioned below the suction nozzle and moved to a position for storing electronic circuit components which have come off and dropped from the suction nozzle, and a position retracted from below the suction nozzle for allowing the lowering of the suction nozzle, by a cylinder. If an electronic circuit component comes off the suction nozzle after a suction nozzle has taken out the electronic circuit component from an electronic circuit component supply device and before the electronic circuit component is mounted on a circuit board, the electronic circuit component is caught by the dropped component storage box to prevent the electronic circuit component dropping on the circuit board.